Carburetor



Dec. l5, 1953 R. ANDERSON ETAL 2,662,758

CARBURETOR Filed Nov. 5, 1949 Patented Dec. l5, 1953 UNITED STATESPATENT OFFICE CARBURETOR Application November 5, 1949, Serial No.125,768

. 4 Claims. 1

Our invention relates to carburetors and :ls more particularly concernedwith a type of carburetor which can be operated in any position.

In modern aircraft practice it is common to utilize carburetors which4will operate in any position. Such carburetors however are intricate,expensive, and cumbersome, and are entirely unsuitable for use withsmall power tools.

A primary object of our invention is to provide a compact, simple,inexpensive, yet efficient carburetor especially adapted for small toolsand similar uses and capable of operating effectively in all positions,r

Another object of our invention is to provide means for overcoming thedifference in the effect of gravity on the operating parts when thecarburetor is in upright and inverted positions and in all positionstherebetween.

Our invention is an improvement on that disclosed and claimed in theapplication of Robert F. Bracke, Serial No. 125,265, filed November 3,1949 having common ownership with applicants assignee.

In the drawing the single figure is an elevational view in section of apreferred form of our invention.

Referring to the drawing it will be seen that our carburetor comprises abody 2 having an air inlet 4 leading to a choke bore 6 provided with anyusual choke valve 8. The choke bore t in turn communicates with aVenturi shaped air passage lil discharging into the throttle bore l2. Athrottle valve I4 which may be of any usual construction is located inthe throttle bore l2. A small vent t6 is provided to prevent floodi ingof the carburetor under any conditions of operation.

A high speed fuel jet I8 is located in the Venturi shaped passage Ill.It is to be noted that this jet, preferably but not necessarily,coincides with the central axis of the passage in the direction of flowof air therethrough and is formed in the wall of a tubular part 20 whichbisects the Venturi shaped passage Ill. A11 idle jet 22 is alsoprovided. For some purposes a third jet 26 may be provided. This fueljet 26 is for the purpose of enriching the mixture at speeds veryslightly above idle and is particularly advantageous where thecarburetor is to be utilized on a four-cycle engine. This jet 26 howeveris not essential and may be dispensed with if desired. f

The carburetor is adapted to be connected to any suitable source of fuelsupply by means of a pipe 2a.threadedlyv attached to a tapered fuelinlet 30 provided in the lower part of the body 2, This inletcommunicates with a chamber 32 formed between a valve seat member 34 anda plug 36. The member 34 has a valve seat 38 adapted to be engaged bythe tapered surface of a main fuel valve t6 which is urged toward itsseat by a spring 42. A float 43 of cork or other suitable material orconstruction is attached to the `downwardly projecting stem 45 of thefuel valve 4U and is designed to balance the pull of gravity on the fuelvalve and its associated stems so that the force with which the springd2 urges the fuel valve toward its seat is not affected by changes inthe position of the carburetor.

The fuel valve 40 has an upwardly projecting stem 44 whose upper end isspaced slightly from the lower end of an operating rod 48 when the partsare in rest position, as shown in the drawing. This operating rod has aflange 48 resting on a spring 50 of just suflicient strength to overcomethe weight of rod 46 and any frictional resistance to movement thereofso that this rod is returned to the position shown independently of themain fuel Valve 40 and offers no resistance to closing movement of thisvalve.

The operating rod 46 passes through the tube 20 and its upper end slidesfreely in the wall 52 just beneath a diaphragm chamber 54 whose lowerpart is formed in the upper end of the body 2. The upper part of thediaphragm chamber 54 is formed by a cover 56 attached to the body 2 byscrews 58 or in any other suitable manner, A diaphragm of flexiblematerial impervious to gasoline and oil has its edge confined betweenthe body 2 and cap 56 and forms a. seal therebetween. The centralportion of the diaphragm 60 is provided with metal plates 62 held inplace by a rivet 64. The lower face of this rivet is positioned toengage the upper end of the actuating rod |26 and move it downwardlyunder the iniiuence of the diaphragm 68 in a manner hereinafter morefully described.

The main fuel valve 48 controls communication between the chamber 32 andradial passages 66 leading to an annular chamber 68. A duct il) connectsthe annular chamber 63 with a high speed orifice I2 controlled by thehigh speed needle valve 13 which is adjustable to vary the effectivesize of the orice 12. Fuel fiowing past the orifice 12 travels by way ofducts 14 and 16, chamber 18, and passageway 89 to the main fuel jet I8.Passage also continues past the main fuel jet and Vconnects with duct 82leadingkto idle orifice 84 which is adjustably controlled by 3 theidling needle valve 86 to regulate the discharge of fuel through idlejet 22. In carburetors also equipped with the jet 26, this jet receivesits fuel from chamber 18 by way of ducts 88 and 90.

A passage 92 connects the lower side of the diaphragm chamber with thefuel duct 10 leading to high speed orifice l2 so that the suctionavailable to move the central portion of the diaphragm 60 downwardly isthe suction existing in thevpassage between the main fuel valve and thehigh speed orifice. This passage 92 also removes from the diaphragmchamber any fuel which may leak thereinto around the upper end of therod 46 and maintains the diaphragm chamber free of fuel so that thediaphragm can accurately and immediately reflect changes in the forcesacting thereon.

inv

A small duct .94 connects the lower part of the..

diaphragm chamber with the choke bore 6 and permits a small quantity ofair to bleed into the diaphragm chamber. This air in turn is sucked outof the diaphragm chamber through duct 92 and mixes with fuel supplied tothe several fuel jets. The small quantity of air entering the diaphragmchamber through duct 94 assists in maintaining the diaphragm chamberperfectly dry and is too small in volume t have any appreciable effecton the supply of fuel to the several jets.

To facilitate starting, particularly in cold weather, we provide what iscommonly known as a tickler. This tickler comprises a plunger 96 havingan enlarged lower end normally positioned immediately above thediaphragm rivet 6&3. The upper end of the plunger is attached to a cap98 resting on a spring |90 which serves to hold the plunger in elevatedposition. The lower end of the spring i rests upon a sleeve l0?. screwedinto the upwardly projecting tubular extension |94 of the cover 55. Thecap 98 may be pressed downwardly by the fingers to open the fuel valveduring a starting operation.

In operation our novel carburetor is attached to the intake manifold ofan engine and to a source of fuel such as a fuel supply tank locatedslightly above the carburetor. Both needle valve:J are open such forexample as one-half to threefourths of a turn, the choke is closed orpartly closed, and if the motor is cold the tickler may be presseddownwardly while the engine is cranked. As soon as the engine starts thetickler is released and the choke is immediately or gradually returnedto the open position shown as determined by temperature and otherstarting conditions.

Air entering the carburetor and flowing through the Venturi shapedpassage lil creates a suction at the high speed jet i8 proportional toengine demand. This suction is communicated to the diaphragm chamberthrough passage 8U, chamber 18, ducts 'i6 and "it, orifice l2 and ducts79 and 92.

The upper side of the diaphragm 6D is subjected to atmospheric pressurethrough the clearance around the plunger 95 of the tickler, and the kerfl on the lower end of the sleeve i02 and the difference in pressure onthe opposite sides of the diaphragm causes the diaphragm to ilexdownwardly and hold the main fuel valve 40 open. If the suction in thediaphragm chamber is increased, as it is at higher engine demand, thediaphragm is flexed to a greater extent and the main fuel valve opens toa correspondingly greater degree.

When the carburetor is in the position shown in the drawing the force ofgravity acting on the fuel valve 4% and its associated stems 44 and 45tends to open this valve but this force is exactly counter-acted by thebuoyancy of the oat 33. If the carburetor is inverted the force ofgravity acting on the valve 4b and its associated stems would tend toclose this valve but is counteracted by the buoyancy of the float i3 vIfthe carburetor is placed in a position with the fuel valve 4G and itsstems 44 and 45 in a horizontal plane, the force of gravity will have notendency to either open or close the valve. Likewise the buoyancy of thefloat 43 will have no tendency to open or close the valve 4B so that inthis position also the spring 42 has no function except to urge thevalve toward closed position. It therefore will be apparent that ournovel construction has the advantage of neutralizing any force exertedby gravity tending to open or close the main fuel valve, so that openingand closing movements of this valve depend solely on the springs i2 and50 and the suction produced in the diaphragm chamber.

The duct Sui allows a small amount of air at atmospheric pressure tobleed into the diaphragm chamber but this inflow of air is not sucientto affect the operation of the diaphragm. The purpose of this air bleedis to keep the diaphragm chamber dry so that the movement of thediaphragm can instantaneously respond to quick changes of the throttleValve and quick changes in engine demand. For some purposes it may beadvantageous to eliminate passage 92 and connect the lower side of thediaphragm chamber with the junction of fuel passages 8i) and 82 byproviding a substantial clearance between the wall 52 and upper end ofthe actuating rod 4G.

It is to be understood that our invention is not limited to theparticular details shown and described but may assume numerous forms andincludes all variations, modifications, and equivalents coming withinthe scope of the appended claims.

We claim:

l. A carburetor of the class described the combination of a bodyproviding an air passage therethrough, jet means for supplying fuel toair flowing through said passage, said body having a fuel inlet, a fuelpassage connecting said inlet with said jet means, a valve in saidpassage for controlling flow of fuel to said jet means, a spring forclosing said valve, means responsive to engine operation for openingsaid valve, and means for overcoming the effect of gravity on said valvefor all positions of said carburetor, said means including a fuelchamber, a float in said chamber, said float being lighter than acorresponding volume of said fuel, and means attaching said oat to saidvalve.

2. In a carburetor of the class described the combination of meansproviding a passage therethrough, jet means for supplying fuel to airflowing through said passage, said first-named means having a fuel inletand providing a conduit connesting said inlet with said jet means, avalve in said conduit for regulating ilow of fuel to said jet means,means responsive to engine operation for opening said valve, othei`means for closing said valve, said conduit including a chamber betweensaid inlet and valve and a float in said chamber for overcoming anyaction of gravity tending to open or close said valve, said float beinglighter than a corresponding volume of said fuel.

3. In acarburetor of the class described the combination of a bodyproviding an air passage therethrough, jet means for supplying fuel toair flowing through said passage, said body having a fuel inlet and afuel passage connecting said inlet with said jet means, a valve in saidconduit controlling flow of fuel to said jet means, automatic means foropening said valve, a second means for closing said valve, and floatmeans balancing the tendency of gravity to open and close said valve,said oat being lighter than a corresponding volume of said fuel.

4. In a carburetor of the class described the combination of a bodyhaving an air passage therethrough, jet means for supplying fuel to airflowing through said passage, said body providing an inlet and a fuelpassage connecting said inlet with said jet means, a valve in said fuelconduit for regulating flow of fuel to said jet means, said valve havingoppositely extending stems, a cork float attached to one of said stems,said oat being located in a part of said fuel passage, a spring actingon said stem to close said valve, diaphragm means operating on the otherstem to open said valve, and means responsive to engine demand forcreating a pressure differential across said diaphragm.

ROBERT ANDERSON. ROBERT F. BRACKE.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 1,933,379 Mock Oct. 31, 1933 2,084,377 Barbarou June 22, 19372,390,658 Mock Dec. 11, 1945

